This application is related generally to geometric structural systems. More specifically, this application is related to geometric modeling kits.
Geometric modeling kits typically comprise a plurality o pieces that may be categorized broadly into two groups: structural nodes and structural connectors. A structural network may be formed from the pieces by interconnecting the structural nodes with the structural connections. For example, U.S. Pat. No. 3,722,153 issued to Stephen C. Baer discloses forming a three-dimensional figure by connection of hall-shaped nodes or connectors and struts into different geometric configurations using the fivefold symmetries of the icosahedron and the dodecahedron. In some instance the structural connections comprise struts, which are elongated structures having ends configured for insertion into selected openings or cavities in the structural nodes. By combining a series of structural nodes and structural connections in different selected angular relationships, a variety of different three-dimensional structures may be constructed. Such geometric modeling kits are commonly used by diverse groups of people, including by children as a form of toy, but also by mathematicians, artists, engineers, and scientists to aid in the study of sophisticated geometric structural systems.
A number of different approaches have been taken to securing the structural connections to the structural nodes, including such inconvenient techniques as welding them together. More commonly, the structural connections and nodes are secured using frictional forces between plastic structures. Plastic is a desirable material for the structural connections and nodes because it is sufficiently flexible to permit deformation of a structural system to allow other components to be added during assembly and is well suited to mass-production molding techniques. When securing the structural connections and nodes with frictional forces, stubs at the ends of structural connections may be formed to have a negative clearance (or interference) with corresponding openings in the structural nodes. However, such a technique results in undesirable stress on models after assembly, increasing the likelihood that some of the components will permanently deform due to stress, and interference makes the models more difficult to build because of resistance to inserting struts in nodes caused by friction. In addition, this resistance may result in incomplete insertion of struts into nodes leading to accumulated dimensional errors that may frustrate users and render larger models difficult or impossible to build.
There is, accordingly, a general need in the art for improved mechanisms for securing components of geometric modeling kits.